We would like to have BB's somehow connect to our mysql database (not via cable/software on desktop); and update address book on BB with data from our database. BB's can also have additional entries outside this app; so completely replacing the address book with a "master" is not an option.

Does any software already already exist to do this?

Here's how the system will work. BB's are used by supervisors. Database contains names and telephone numbers of line staff; we use categories to identify which depts line staff are trained to work in. Supervisors receive calls from employee calling in sick or some other type of absence. This should be employee's home number; so name from address book should appear on display. Supervisor then accesses address book for other staff already trained in dept (categories) and starts making calls until replacement worker is found. On nights/weekends, one supervisor in five are "on call" and actually do this function for other 4 supervisors within their "cluster".

We currently use paper (one page per dept) to list all line staff trained in a location; and their current contact info.